Comparative Study of the Effects of Wildfire and Cultivation on Topsoil Properties in the Zagros Forest, Iran

This study compares the long-term effects of a wildfire on basic topsoil properties—bulk density, particle-size composition, pH, electrical conductivity, total C and N, inorganic C, cation exchangeable capacity, available N, P, Ca, Mg, and K—in the Zagros oak forest, Iran, with those induced by agricultural activity in a vineyard planted 30 years earlier in place of the forest. The soil, Calcaric Cambisol according to the World Reference Base, was studied in the (i) unburned forest, both inside (FI) and outside (FO) sprout clumps; (ii) burned forest, in areas subjected to high (BHI) or moderate (BMI) severity (both inside sprout clumps) and low (BLO) severity (outside sprout clumps); and (iii) vineyard, both under the foliage of vines (VI) and outside it (VO). In VI, VO, BHI and BMI most soil properties were significantly different from those of the unburned forest. A Hierarchical Cluster Analysis grouped together BHI and BMI and separated their unburned counterparts with 72% and 47% dissimilarity, respectively. The VI and VO treatments in the vineyard were closely related to each other, but separated from their unburned counterparts in the unburned forest soil with 149% and 69% dissimilarity, respectively. Overall, thirty years of farming exerted a stronger impact on the soil than a single, though severe, fire. Nevertheless, severe fire appeared to have a much more significant impact than every single yearly plowing.